Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters

Abstract

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1-different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2-the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scann ing speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach

Dental tissue ablation by means of a picoseconds laser

“…On the other hand Er:YAG lasers are affected by cumbersome instrumentation, and operation durations can be higher than the ones of traditional instruments. Records of dental surface treatment with ultra-short pulsed lasers, 150 -500 fs, are also present, at such pulse duration remarkable results have been obtained, regardless to the laser emission wavelength [6,7].…”

Investigations of the damage mechanisms during ultrashort pulse laser ablation of dental tissue

“…A discussion about how the ablation rate can be scaled using ultrashort pulse lasers can be found in several publication [7][8][9]. Recently, Schelle et al demonstrated that the ablation rate scales linear with power up to 50 W at a repetition rate of 500 kHz, enabling removal rates of up to 50 mm³/min [10].…”

In Vivo Femtosecond Ablation and Imaging in Bone with a High Repetition Rate Source

“…Despite these potential advantages, primary oscillators have only recently attained pulse energy levels such that plasma-mediated ablation of biological materials is possible without amplification [6,7]. Regenerative amplifiers are sensitive, expensive, and bulky, and serve as a high barrier to entry for those focused primarily on biological imaging.…”